1. Field of the Invention
The invention relates to connections between integrated circuits and a supporting substrate such as a printed circuit board. More particularly, the present invention relates to an interposer for coupling an integrated circuit to a supporting substrate.
2. Background
Integrated circuits have been manufactured for many years. Conventionally, such manufacturing involves integrating various active and passive circuit elements into a piece of semiconductor material, referred to as a die, and the die is encapsulated into a ceramic or plastic package. These packages are then typically attached to a printed circuit board by connecting pins, arranged along the periphery of the package. An electronic system can be formed by connecting various integrated circuit packages to a printed circuit board.
As advances in semiconductor manufacturing technology led to substantially increased numbers of transistors on each integrated circuit, it became possible to correspondingly increase the functionality of each integrated circuit. In turn, increased functionality resulted in the need to increase the number of input/output (I/O) connections between the integrated circuit and the rest of the electronic system of which the integrated circuit was a part. One adaptation designed to address the increased need for I/O connections was to simply add additional pins to the package. Unfortunately, adding pins to the package increased the area consumed by the package. A further adaptation designed to address the increased need for I/O connections without consuming an unacceptably large amount of area was the development of pin grid array (PGA) and ball grid array (BGA) packages. In such a package, a large number of I/O connection terminals are disposed in a two dimensional array over a substantial portion of a major surface of the package. These PGA and BGA packages typically contain an integrated circuit die, and are attached to a supporting substrate such as a printed circuit board.
Although PGA and BGA packages provide a space-saving solution for integrated circuits needing a large number of I/O connections, the materials from which they are manufactured typically do not provide a good match with the material of the integrated circuit die in terms of their respective coefficients of thermal expansion.
What is needed is a structure suitable for electrically and mechanically coupling an integrated circuit to a supporting substrate wherein the structure has thermal expansion characteristics well-matched to the integrated circuit. What is further needed is a method of manufacturing such a structure.